Technical Field
This disclosure relates to an automatic document feeder having a driving release mechanism that releases transmission of a driving force between a roller that conveys an original document and a driving source, an image reading device that incorporates the automatic document feeder, and an image forming apparatus that incorporates the image reading device.
Related Art
Various types of image reading devices are known to include an automatic document feeder (hereinafter, referred to as an ADF) including a document table on which an original document is set, a conveying unit that conveys the original document, and a sheet ejection tray that ejects a read original document to separate and convey the original documents set on the document table one by one and to consecutively perform reading.
The ADF conveys the original document by connecting a sheet conveying roller and a motor as the driving source through gears and driving the sheet conveying roller. As the gear attached to the motor, in general, a spur tooth gear or a helical gear is used. However, in recent years, since quietness of the device is required, a configuration of driving where a worm gear having higher quietness is attached to a motor has appeared.
As a feature of the configuration using the worm gear, there is a self-lock function of the worm gear. The self-lock function is a function where the worm gear side can transmit a driving force to rotate the sheet conveying roller but the opposite side, that is, the sheet conveying roller side is locked and therefore cannot rotate the worm gear.
In general, in the ADF, when jam (paper jam) of the original document occurs during sheet conveyance, a user opens a document feeder cover that functions as a portion of a conveying passage and removes the original document by turning a paper jam handling dial provided to pull out the original document by hand. At this time, if the worm gear is connected to a drive system, due to the above-described self-lock function, the worm gear is not allowed to be rotated by the sheet conveying roller side, namely, the sheet conveying roller is locked, so that paper jam handling cannot be performed.
In order to address this inconvenience, known ADFs have a configuration including a driving release mechanism disconnecting transmission of the driving force between the worm gear and the sheet conveying roller in association with the opening operation, at the time of opening the document feeder cover for paper jam removal, so that the sheet conveying roller is not locked.
The driving release mechanism has a configuration, for example, in which a gear (hereinafter, referred to as a drive release gear) that is moved by a spring force in association with the opening operation of the document feeder cover and an idler gear that is connected to the worm gear are attached coaxially. In addition, the driving release mechanism is provided with meshing portions having pawls, projections, or gears that are provided so as to be meshed with the drive release gear and the idler gear. In the driving release mechanism having the configuration, transmission and release of the driving force are implemented by the drive release gear and the idler gear engaging (connecting) or releasing engagement of the meshing portions.
In addition, in the known ADFs, for example, as a device transmitting a driving force of a motor used for a process cartridge, a device including a plurality of involute spline joints are provided, and each involute spline joint is engaged with an involute spline joint of a driven side through meshing, so that a driving force for rotation is transmitted.